We, the present inventors, already provided istamycins A, B, A.sub.o and B.sub.o as the aminoglycosidic antibiotics which are produced by a microorganism, Streptomyces tenjimariensis of the actinomycetes (Japanese patent application first publication "Kokai" Nos. 14569/80 and 43295/81; U.S. Pat. No. 4,296,106; U.K. Pat. No. 2,048,855B); istamycins C and C.sub.o (Japanese patent application first publication "Kokai" No. 118598/82); istamycins A.sub.1, B.sub.1, C.sub.1 and A.sub.2 (Japanese patent application first publication "Kokai" No. 139092/82); and 2"-N-formimidoylistamycins A and B (Japanese patent application No. 80218/82; Japanese patent application first publication "Kokai" No. 198298/83; U.S. Pat. No. 4,382,926; U.K. Pat. No. 2,088,851B). Amongst these istamycins, istamycin B is of the highest antibacterial activity. We have further studied istamycin B to produce some derivatives therefrom, and succeeded to synthesize 3-O-demethylistamycin B which is active against resistant bacteria, Pseudomonas aeruginosa and also against a variety of resistant strains of gram-negative and gram-positive bacteria (Japanese patent application first publication "Kokai" No. 50996/82; U.S. Pat. No.4,499,083; European Pat. No. 0048549). Although the various derivatives of istamycin B which were already provided by us are useful as antibacterial agent, they are not necessarily an antibacterial agent which is satisfactory completely, and they are reported to have innegligible acute toxicity. In these circumstances, it is still demanded to provide any new derivatives of istamycin B which show lowered acute toxicity with maintaining the high antibacterial activity of the parent istamycin B.